The search for extraterrestrial life in our Solar System has become more exciting. A team of scientists, including Dr. Christopher Glein from the Southwest Research Institute, has discovered new evidence that Saturn‘s moon’s underground ocean contains a key element for life.
The team detected on Enceladus phosphorus in the form of phosphates originated from the moon’s global ocean covered in ice, using data from NASA‘s Cassini mission. Cassini explored Saturn and its system of rings and moons for over 13 years.
From models to discovery
“In 2020, we used geochemical modeling to predict that phosphorus should be abundant in Enceladus’ ocean” said Glein, one of the leading experts in extraterrestrial oceanography. Co-author of an article in the journal Nature (ref.) describing this research. “Now, we have found abundant phosphorus in the ice plume samples that emerge from the subsurface ocean”.
The Cassini probe discovered liquid water beneath the surface of Enceladus. The analyzed samples came from an ice and gas plume ejected into space from cracks on the moon’s icy surface. Analysis using Cassini’s cosmic dust analyzer showed the presence of sodium phosphates. The team’s observational results, along with laboratory analog experiments, suggest that phosphorus is readily available in Enceladus’ ocean in the form of phosphates.
Phosphorus in the form of phosphates is vital for all life on Earth. It is essential for the creation of DNA and RNA, for energy-carrying molecules, for cellular membranes, bones and teeth in humans and animals, and even for the marine microbiome of plankton. Life as we know it simply cannot exist without phosphates.
Oceanic habitable worlds
“We found concentrations of phosphates at least 100 times higher in the oceanic waters forming the moon’s plume than in Earth’s oceans” said Glein. “Using a model to predict the presence of phosphate is one thing, but actually finding the evidence for phosphate is incredibly exciting. This is an extraordinary result for astrobiology and a significant step forward in the search for life beyond Earth”.
We are witnessing the most important discovery in planetary science in the last 25 years. Worlds with oceans beneath a superficial layer of ice are common in our Solar System. These planets include the icy satellites of the giant planets, such as Europa, Titan, and Enceladus, as well as more distant bodies like Pluto. Worlds like Earth with surface oceans occur within a narrow range of distances from their host stars to maintain liquid water. However, inner oceanic planets can occur over a much wider range of distances. This greatly expands the number of habitable worlds that could exist in the Milky Way.
“Geochemical experiments and modeling demonstrate that such high concentrations of phosphate result from increased mineral solubility of phosphate in Enceladus and perhaps in other icy oceanic worlds in the solar system beyond Jupiter” Glein said. “With this discovery, Enceladus’ ocean is now known to meet what is generally considered the most stringent requirement for life. The next step is clear: we must return to Enceladus to see if the habitable ocean is actually inhabited”.